How It Works

The years to FI calculation considers your current savings, annual contribution, expected returns, and target FIRE number. The NPER function calculates how many periods until you reach your goal.

The Formula

=NPER(annual_return, -annual_savings, -current_savings, fire_number)

Or for monthly contributions:

=NPER(annual_return/12, -monthly_savings, -current_savings, fire_number) / 12

Example

Your Situation:

Current Savings: $150,000
Annual Savings: $35,000
Expected Return: 7%
FIRE Number: $1,250,000

Years to FI:

=NPER(7%, -35000, -150000, 1250000) = 14.8 years

You’ll reach FI in about 15 years.

Quick Reference Table

Time to $1,000,000 (7% return)

Starting Amount	Annual Savings	Years to FI
$0	$20,000	24.2
$0	$30,000	19.3
$0	$40,000	16.1
$0	$50,000	13.8
$50,000	$30,000	16.4
$100,000	$30,000	14.1
$150,000	$30,000	12.1
$200,000	$30,000	10.3

Building a Years-to-FI Calculator

Input	Value
Current Age	32
Current Savings	$150,000
Annual Income	$95,000
Annual Expenses	$50,000
Annual Savings	=B3-B4
Savings Rate	=B5/B3
Expected Return	7%
FIRE Number	=B4*25

Output	Formula
Years to FI	`=NPER(B7, -B5, -B2, B8)`
FI Age	`=B1+B9`
FI Year	`=YEAR(TODAY())+B9`

Results:

Annual savings: $45,000
Savings rate: 47%
FIRE number: $1,250,000
Years to FI: 13.6
FI Age: 45.6
FI Year: 2039

The Savings Rate is Key

Your savings rate is the most important factor in time to FI:

=annual_savings / annual_income

Savings Rate	Years to FI (starting $0)
10%	51 years
20%	37 years
30%	28 years
40%	22 years
50%	17 years
60%	12.5 years
70%	8.5 years
80%	5.5 years

Assumes 5% real return, expenses stay constant

Impact of Variables

Effect of Return Rate

$200K saved, $40K/year savings, $1.2M target:

Return Rate	Years to FI
5%	14.9
6%	13.8
7%	12.9
8%	12.1
9%	11.4

Each 1% return difference = ~1 year.

Effect of Starting Amount

$40K/year savings, 7% return, $1.2M target:

Starting Amount	Years to FI
$0	17.1
$100,000	14.0
$200,000	11.2
$300,000	8.6
$400,000	6.2

Starting earlier matters enormously.

Effect of Savings Amount

$200K saved, 7% return, $1.2M target:

Annual Savings	Years to FI
$20,000	20.9
$30,000	15.8
$40,000	12.9
$50,000	10.9
$60,000	9.4

Monte Carlo Reality Check

Historical returns vary. Consider ranges:

Scenario	Avg Return	Years to FI
Bear Market	4%	16.8
Conservative	5%	14.9
Average	7%	12.9
Bull Market	9%	11.4

Plan for the conservative case; celebrate if you get average or better.

Year-by-Year Projection

Track your progress:

Year	Starting	Growth	Savings	Ending
1	$150,000	$10,500	$40,000	$200,500
2	$200,500	$14,035	$40,000	$254,535
3	$254,535	$17,817	$40,000	$312,352
5	$382,469	$26,773	$40,000	$449,242
10	$728,547	$50,998	$40,000	$819,545
13	$1,046,890	$73,282	$40,000	$1,160,172

Formulas for each year:

Growth: =previous_ending * return_rate
Ending: =previous_ending + growth + annual_savings

Accelerating Your Timeline

Increase Income

Every $10K raise (50% saved):

=-NPER(7%, -45000, -150000, 1250000) + NPER(7%, -50000, -150000, 1250000)
= saves ~1.4 years

Decrease Expenses

Every $5K expense reduction:

Save $5K more annually
Need $125K less ($5K × 25)
Double impact on timeline

Windfalls

Bonus, inheritance, or windfall of $50K:

=NPER(7%, -40000, -200000, 1250000) vs NPER(7%, -40000, -150000, 1250000)
= saves ~2.0 years

The Three Phases of FI

Phase 1: Building (Years 1-5)

Focus on increasing income
Maximize savings rate
Compound growth is small

Phase 2: Growth (Years 5-10)

Compound growth becomes significant
Portfolio growth may exceed contributions
Stay the course

Phase 3: Home Stretch (Final years)

Market returns matter most
Consider derisking slightly
Plan the transition

Sensitivity to Expense Estimates

Your FIRE number depends on expense assumptions:

If Expenses Are Off By	FIRE Number Change	Years Change
+$5,000/year	+$125,000	+2-3 years
+$10,000/year	+$250,000	+4-5 years
-$5,000/year	-$125,000	-2-3 years
-$10,000/year	-$250,000	-4-5 years

Track expenses carefully - small errors compound.

Multiple Paths to FI

Same $1.2M target, different approaches:

Strategy	Income	Expenses	Savings Rate	Years
High Income	$150K	$70K	53%	12
Frugal	$75K	$35K	53%	12
Balanced	$100K	$50K	50%	13
Side Hustle	$80K + $20K	$50K	50%	13

Different paths, similar timelines - focus on what works for you.

Coast FI Milestone

Calculate when you can stop saving and still reach FI by target age:

=fire_number / (1 + return)^years_until_target_fi_age

Example: $1.2M target, want to retire at 55, currently 35:

=$1,200,000 / (1.07)^20 = $310,178 Coast FI number

Once you hit $310K, you could theoretically stop saving and reach $1.2M by 55.

Withdrawal Phase Considerations

As you approach FI, consider:

Years to FI	Consideration
10+ years	Stay aggressive, focus on growth
5-10 years	Start thinking about asset allocation
2-5 years	Begin shifting some to bonds
<2 years	Build cash buffer for sequence risk

Early Retirement Age Reality Check

FI Age	Years in Retirement	Withdrawal Rate
65	25-30	4%
55	35-40	3.5%
45	45-50	3-3.5%
35	55-60	3%

Earlier retirement = longer timeline = more conservative withdrawal rate needed.

Pro Tips

Use conservative returns - plan for 5-6% real returns; 7% is optimistic
Recalculate annually - update your timeline with actual numbers each year
Focus on savings rate - it’s the variable you control most
Consider tax diversification - mix of traditional/Roth affects actual timeline
Build in buffer - aim for 110% of your FIRE number for margin

Common Errors

Ignoring inflation - either use real returns (~4-5%) or inflate expenses
Assuming constant returns - markets don’t return 7% every year; expect volatility
Not adjusting savings - as income grows, savings should too
Forgetting about healthcare - early retirees need to budget for this
Starting over after withdrawal - taking money out resets your timeline significantly

Years to Financial Independence